Research has demonstrated that children who were exclusively breastfed perform better on tests of cognitive function and intelligence than those who were exclusively formula-fed, even after controlling for potential other explanations (such as socioeconomic status, gestational duration, birth weight, maternal education, and educational opportunities).

There also seems to be a link not just between IQ and whether or not a child was breastfed but also between IQ and the length of breastfeeding, with more breastfeeding correlating with higher IQ (up to a point). Additionally, adolescents who had been exclusively breastfed as infants have thicker cortex in the parietal lobes (involved in many cognitive functions including visuospatial tasks, mathematics, and attention) as well as more white matter (the “wiring” between areas of the brain).

Researchers in a new study from Brown University looked at the white matter of 133 children aged 10 months to 4 years in order to understand if there are early differences in brain development, depending on whether the children had been breastfed.

The study participants were placed in three groups:

Those who had been exclusively breastfed for at least 3 months

Those who were exclusively formula fed, or

Those who received a mixture of breast milk and formula

Children were scanned in MRI machines while they slept, in order to reduce what are called motion artifacts (distortions of images caused by movement). Then the white matter of the children in the three groups was compared to each other. What the researchers found was striking.

Different areas of the brain mature and develop at different rates. White matter in the brain appears white because the neurons in this area of the brain are covered in sheaths of insulating fat (myelin) that work much like insulation around electrical wire, protecting them but also allowing them to send signals more quickly. As the human brain develops, areas of white matter are myelinated at different speeds and different times, continuing into at least a person’s early to mid 20s. Frontal areas of the brain and areas involved in complex cognitive tasks (planning, language, organizing) develop latest with simpler areas of the brain developing earlier.

With this new study, the researchers found that early exclusive breastfeeding was associated with increased development in areas of the white matter that develop and mature last. These regions and connections that had increased development in breastfed children are commonly associated with complex cognitive tasks, including executive functioning, social–emotional functioning, and language. In addition, breastfed infants were found to have improved performance in these cognitive domains. Other areas of the brain in infants exclusively breastfed also showed more development, including areas involved in language performance, visual reception, and motor control.

Based on the findings of this study and other large-scale, exclusively breastfeeding clearly is associated with better brain development early in life and at least into adolescence. Being exclusively breastfed is also associated with higher IQ scores and better performance on cognitive tasks.

Length of breastfeeding is also important, with evidence supporting the benefits for continuing to breastfeed for at least the first two years of a child’s life. What is not known is why breast milk is so much better than formula, or if there is some other as yet undiscovered factor that is the real benefit. Based on these findings, it can be important at the individual, family, community, and societal levels to reduce pressures on mothers to reduce the length of exclusively breastfeeding their children.

Jared Tanner has a Ph.D. in clinical psychology with an emphasis in neuropsychology. His interests are mainly neuroimaging and neuroanatomy. He spends his research time looking at the structure of gray and white matter in the brains of people with Alzheimer's disease and Parkinson's disease. With a focus on neuropsychology, he is also interested in how normal and abnormal brain structure relates to cognitive and behavioral functioning.

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